1. Field of the Invention
The present invention relates to a gateway device, a radio base station device, a router device and a radio terminal device, which are to be used in radio communications utilizing the transport layer.
2. Description of the Background Art
In recent years there are increasing demands for carrying out not just speech communications but also data communications by radio. TCP (Transmission Control Protocol) is widely used as a reliable transport layer protocol in the wire data communications, but the direct application of this protocol to radio communications causes the following problems.
A TCP segment loss in the wire communications implies the congestion of a network so that TCP is designed to avoid the congestion by lowering a data transmission rate when the segment loss is detected. For this reason, the TCP segment loss due to a radio section error and a handoff will also be interpreted as the congestion so that the congestion avoidance operations will be executed more than necessary and as a result the throughput will be lowered more than necessary.
In order to resolve this problem, there is a proposition to use the usual TCP in a wire network and the radio transport layer in a radio network and relay communications at a border between the wire network and the radio network. For example, xe2x80x9cselective ackxe2x80x9d is used for a high segment loss rate on the radio network side. Namely, this is a scheme for resolving the congestion problem in such a way that a data loss in the radio section is not regarded as the congestion and a re-transmission is carried out without lowering the transmission rate.
Also, in TCP, when an idle connection state, i.e., a state where no response comes from a terminal on one side and no response comes from a terminal on the other side as well, is continued for two hours, a keep-alive packet will be transmitted by a server terminal in which a keep-alive option is set valid. If there is no response to this keep-alive packet which is an inspection packet, the transmission of this keep-alive packet will be continued at 75 seconds interval, but when ten consecutive trials fail, it is judged that a terminal on the client side is inactive and the connection will be disconnected.
As described, in the case of carrying out communications between a radio terminal device accommodated in a radio network and a wire terminal device accommodated in a wire network, a gateway device for relaying the transport layer protocol cannot directly ascertain the radio communication state of the radio terminal that terminates the transport layer connection, so that there has been a problem that it is impossible to realize the adaptive control of the transport layer connection (such as a dynamic change of a segment size) according to the radio communication state or property.
It is therefore an object of the present invention to provide a communication scheme for improving the performance of communications utilizing the transport layer connection provided via a radio network, by enabling a control of the transport layer connection according to the radio communication state and property of the radio terminal, without changing implementation of the transport layer of a terminal connected to a wire network, so as to resolve the above described problems that arise when a reliable transport layer protocol is applied to a radio network.
Specifically, the present invention provides a gateway device, a radio base station device, a router device, and a radio terminal device for this communication scheme.
According to one aspect of the present invention there is provided a gateway device, including: a conversion unit configured to bidirectionally convert a first transport layer protocol used for communications within a radio network and a second transport layer protocol used for communications within a wire network, in a case of carrying out communications between a radio terminal device accommodated in the radio network and a wire terminal device accommodated in the wire network; and a control unit configured to control a connection in the first transport layer protocol according to an information regarding a radio communication state of the radio terminal device.
According to another aspect of the present invention there is provided a router device, to be connected with a plurality of radio base station devices for accommodating a radio terminal device located within radio service areas and a wire network to which a wire terminal device is connected, for carrying out data transfer between the radio terminal device and the wire terminal device, the router device comprising: a correspondence setting unit for bidirectionally converting a first transport layer protocol used for radio communications and a second transport layer protocol used for wire communications in a case of carrying out communications between the radio terminal device and the wire terminal device, and setting the radio terminal device in correspondence to one of a plurality of gateway devices for controlling a transport layer connection in the radio communications according to a radio communication state of the radio terminal device; and a transfer unit for receiving a packet from one radio base station that contains at least identifier of the radio terminal device and an information regarding the radio communication state of the radio terminal device that is located in a radio service area of said one radio base station, and transferring said packet to one gateway device that is set in correspondence to the radio terminal device by the correspondence setting unit.
According to another aspect of the present invention there is provided a radio base station device, comprising: a processing unit for carrying out a base station processing necessary in accommodating a radio terminal device located in a radio service area; and a notification unit for notifying an information regarding a radio communication state of the radio terminal device located in the radio service area, to one of a router, a gateway, and a home location register.
According to another aspect of the present invention there is provided a radio terminal device accommodated in a radio network, the radio terminal device comprising: an acquisition unit for acquiring an information regarding a radio communication state of the radio terminal device; and a disconnection unit for disconnecting a transport layer connection with a radio base station, when communications with the radio base station are not resumed within a prescribed period of time after receiving the information regarding the radio communication state of the radio terminal device which contains a signal indicating that communication with the radio base station are interrupted.
According to another aspect of the present invention there is provided a radio terminal device accommodated in a radio network, the radio terminal device comprising: an acquisition unit for acquiring an information regarding a radio communication state of the radio terminal device; a re-transmission timer for indicating a timing for a packet to be re-transmitted; and a unit for resetting the re-transmission timer and immediately re-transmitting said packet to be re-transmitted, upon receiving the information regarding the radio communication state of the radio terminal device which contains a signal indicating that communications with the radio terminal device are resumed.
Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.